Table 4.

Association of intensive care unit (ICU) admission with 30 day mortality

Model	Absolute 30 day mortality, % (95% CI)	P value
Unadjusted results
ICU	18.2	-
Non-ICU	13.8	-
Adjusted model *
ICU	17.0 (16.7 to 17.3)	Reference
Non-ICU	16.5 (16.1 to 16.9)	0.04
Instrumental variable model †
ICU	14.9 (13.1 to 16.7)	Reference
Non-ICU	21.0 (17.1 to 25.0)	0.04

^*Adjusted for characteristics of patients and hospitals in table 2 and table 3. Standard errors adjusted for clustering of patients within hospitals.

^†Two stage least squares regression of all patients, using differential distance to nearest hospital with high ICU admission rates as instrumental variable, adjusted for characteristics of patients and hospitals in table 2 and table 3. Standard errors adjusted for clustering of patients within hospitals.